DETECTION  OF  QUINIA. 
335 
cence  of  the  sulphate  of  quinia  is  a,  finer  agent  for  discovering 
its  presence  than  all  other  known  reagents  for  quinia.  Induced 
by  the  wonderful  sensibility  of  spectral  analysis  for  the  discov- 
ery of  many  substances,  I  sought  the  limit  of  fluorescence  of  a 
quinine  solution,  and  found,  to  my  astonishment,  a  most  extra- 
ordinary intensity.  One  is  able  to  discover  through  the  reaction 
of  ammonia  and  prussiate  of  potash  l-8000th  to  l-10,000th  of 
quinia.  When  sulphuric  acid  is  in  excess,  the  fluorescence  is  ob- 
servable if  there  be  but  l-100,000th  of  quinia  present,  when  you 
fill  a  common  test  tube  with  the  solution,  expose  it  to  the  sun- 
light, and  hold  a  piece  of  black  paper  against  it.  At  a  higher 
dilution  the  fluorescence  disappears  to  the  eye  altogether,  but 
it  becomes  visible  at  once,  if  a  pencil  of  rays  is  made  to  fall  ver- 
tically, or  even  obliquely  through  the  tube  when  the  outline  of 
the  converging  rays  is  clearly  observable,  when  the  solu. 
tion  of  sulphate  of  quinia  contains  only  l-200,000th  of  alkaloid. 
Yet  this  reaction  is  so  extremely  acute,  that  by  very  favorable 
light  and  a  careful  manner  of  proceeding,  (strong  magnifying 
tube  of  the  utmost  possible  focal  distance,  pure  white  glass,  and 
dark  background,),  the  l-400,000th  to  the  l-500,000th  becomes 
visible.  In  this  way  one  can  absolutely  discover  l-2000th  to 
l-4000th  part  of  a  milligramme  of  quinine.  This  extraordinary 
sensibility  exceeds  anything  that  the  analysis  of  the  alkaloids 
has  furnished  to  this  time,  the  reactions  of  strychnia  only  show- 
ing a  close  approach  to  such  great  acuteness.  The  simplicity 
and  certainty  of  this  test  compares  favorably  with  the  spectral 
analysis,  which  shows  only  a  much  greater  sensibility  for  so. 
dium,  strontium,  and  calcium  ;  while,  for  instance,  the  spectral 
analytical  reaction  reaches  its  limit  for  copper  at  l-275th  milli- 
gramme, and  for  potassium  and  boracic  acid  at  l-1000th  milli- 
gramme. 
It  seems  that  so  sensitive  a  reaction  for  quinine  is  of  no  prac- 
tical utility,  but  this  is  no  reason  that  it  should  be  over- 
looked. 
In  conclusion,  I  will  observe,  that  aesculin  and  chlorophylle 
behaves  in  the  same  manner  in  reference  to  light. —  Witts.  Vier- 
teljahresschrift,  1862. 
F.  L.  J. 
